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Controlled Acoustic Bass System (CABS) A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms

A new method for improving the low-frequency response in small- and medium-sized rooms uses a pair of front loudspeakers for initiating a traveling plane wave and a canceling rear pair of loudspeakers that effectively remove the acoustic reflection of the back wall. The rear loudspeakers receive a delayed and opposite phase version of the signal presented to the front loudspeakers, thereby canceling the plane wave when it reaches the rear of the room. Unlike equalization techniques that emphasize a single sweet spot, this approach covers the entire room. The upper frequency limit of the system is higher for smaller rooms. Based on an evaluation in two rooms, the system works as intended. Using this method, listeners experience a clear bass sound image, and the rear loudspeakers are inaudible.